'07 YZ450 fork issues

Knowledge seeker

We have a group of vet riders & some of them don't know how to speak english so they ask for my help to ask you guys questions. We need help to find out what is happenning with the front forks. I mean they're so messed up we'd like to know starting ballpark settings to start from scratch. Since he bought the bike used, the previous owner didn't give him the owner's manual. One of the things we did we put a tie wrap around his lower fork tube to gauge how much travel he's using. When he lands from a big jump he feels the forks slams all the way down as if they've bottomed out but the tie wrap doesn't go past 2/3 of the travel.

This is his current setup:
-10 wt oil in both inner & outer fork chambers.
-Reb- 10 clicks out
-Comp-17 clicks out
-He had 375 cc's in both tubes initially but we took out about 3.5 oz at the track.
-The forks are sprung for his weight (210 lbs.)

grayracer513

The base amount of oil for the outer chamber of that fork is 355cc, which can be varied from 300-380cc. I find 320-330 works best for me.

10wt is too heavy by a lot. The fork uses 5 wt oil (anything between 2.5 and 6 is OK) in the inner cartridge, and if you're using 10wt on the inside, that could be your whole problem. A slightly heavier oil, like a 7wt, is OK to use in the outer chambers if you use it at a lower level, like around 320.

You'll find the base settings in section two of the manual. By the sound of things, I would do a complete oil change first. This will give you an opportunity to check for a broken free piston in the inner chamber, which could also cause some of your troubles. The pistons are replaceable separately, but not through Yamaha.